Immunohistochemistry (IHC) employs specific binding agents, such as antibodies, to detect an antigen of interest that may be present in a tissue sample. IHC is widely used in clinical and diagnostic applications, such as to diagnose particular disease states or conditions. For example, particular cancer types can be diagnosed based on the presence of a particular marker molecule in a sample obtained from a subject. IHC is also widely used in basic research to understand biomarker distribution and localization in different tissues.
Biological samples also can be examined using in situ hybridization (ISH) techniques, such as silver in situ hybridization (SISH), chromogenic in situ hybridization (CISH) and fluorescence in situ hybridization (FISH), collectively referred to as ISH. ISH is distinct from IHC, in that ISH detects nucleic acids in tissue sections whereas IHC detects proteins.
As IHC and ISH methods are becoming increasingly important in research and clinical settings, as is the ability to detect multiple targets at once, such as dual detection of a nucleic acid sequence and protein or multiple proteins or nucleic acids on a single sample. For example, a dual gene/protein detection system would allow gene and protein detection on the same slide in one automated run as opposed to two separate runs. However, current detection systems do not adequately provide for detection of multiple targets, such as dual gene/protein detection, on the same slide because IHC and ISH procedures are frequently incompatible with one another.